Generalize mapping provider

Author: Soroosh Sarabadani

operator-framework/src/main/java/io/javaoperatorsdk/operator/ClassMappingProvider.java

@@ -0,0 +1,55 @@
+package io.javaoperatorsdk.operator;
+
+import org.apache.commons.lang3.ClassUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.URL;
+import java.util.*;
+import java.util.stream.Collectors;
+
+
+class ClassMappingProvider {
+    private static final Logger log = LoggerFactory.getLogger(ClassMappingProvider.class);
+
+    static <T, V> Map<T, V> provide(final String resourcePath, T key, V value) {
+        Map<T, V> result = new HashMap();
+        try {
+            final var classLoader = Thread.currentThread().getContextClassLoader();
+            final Enumeration<URL> customResourcesMetadataList = classLoader.getResources(resourcePath);
+            for (Iterator<URL> it = customResourcesMetadataList.asIterator(); it.hasNext(); ) {
+                URL url = it.next();
+
+                List<String> classNamePairs = retrieveClassNamePairs(url);
+                classNamePairs.forEach(clazzPair -> {
+                    try {
+                        final String[] classNames = clazzPair.split(",");
+                        if (classNames.length != 2) {
+                            throw new IllegalStateException(String.format("%s is not valid Mapping metadata, defined in %s", clazzPair, url.toString()));
+                        }
+
+                        result.put(
+                                (T) ClassUtils.getClass(classNames[0]),
+                                (V) ClassUtils.getClass(classNames[1])
+                        );
+                    } catch (ClassNotFoundException e) {
+                        throw new RuntimeException(e);
+                    }
+                });
+            }
+            log.debug("Loaded Controller to CustomResource mappings {}", result);
+            return result;
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static List<String> retrieveClassNamePairs(URL url) throws IOException {
+        return new BufferedReader(
+                new InputStreamReader(url.openStream())
+        ).lines().collect(Collectors.toList());
+    }
+}